One-dimensional, carbon-based, nano-structured materials, which are formally derived from the rolling up of single or multiple graphene sheets into tubular structures, are generally divided into three categories (based on diameter dimensions): single-wall carbon nanotubes (“SWNT”) having diameters ranging from 0.7 nm to 3 nm; multi-wall carbon nanotubes or CNT having diameters ranging from 2 nm to 20 nm; and carbon nanofibers (“CNF”) having diameters ranging from 40 nm to 100 nm. The length of vapor grown carbon nanofibers (“VGCNF”) may range from 30 μm to 100 μm. While the length of SWNT and CNT is difficult to determine because of a strong proclivity to aggregate or form ropes, the lengths of SWNTs and CNTs are generally considered to be two-orders of magnitude shorter than VGCNFs.
Carbon nanomaterials have captivated wide-spread attention in the advanced materials research community because of the predicted extraordinary thermal, mechanical, and electrical properties. To take advantage of their predicted mechanical properties, several studies have been performed on CNT or CNF and reported their reinforcement effects in various thermoplastics and thermoset matrices.
Great strides have been made in the functionalization of SWNT to impart solubility and processing options. Similar to fullerene derivatization chemistry, the general nature of chemical reactions utilized in conventional CNT functionalization are compatible with the electron-deficient character of the carbon nanotubes. This generalization is understandably applicable to the reaction chemistry involving the perfect graphene framework. However, defect sites, (for example, the pre-existing sp2 C—H bonds), of these graphene-based nanomaterials may behave differently.
Graphene-based nanomaterials have such broad applications because of particular thermal, electrical, mechanical, and photonic properties. Therefore, graphene-based nanomaterials are actively investigated with respect to their structural reinforcement, energy/electron transport or storage capabilities, and interactions with electromagnetic waves.
The chemical medication of graphene-based surfaces and edges is usually quantitatively assessed by using the combination of thermogravimetric analysis (“TGA”) and elemental analysis. Experimentally, under TGA conditions, organic functional groups are thermally degraded at temperatures well below the thermal degradation of carbon nanomaterials (much greater than 600° C.). Therefore, the total amount of the specific organic group in the original test sample can be estimated by the associated weight loss. Such estimation is referred to as degree of functionalization (DF or τ and expressed in terms of atom %). It follows that a rough, empirical formula for the functionalized carbon nanomaterial sample may be derived and elemental analysis based on this empirical formula is used for its confirmation. For example, when VGCNF is functionalized via a Friedel-Crafts acylation reaction, the DF for VGCNF is estimated to be 3 atom %, that is to say, on average for every 100 carbon atoms of a single nanofibers, there are 3 functional group grafted.
Therefore, it would be desirable to transfer one or more of these properties to polymeric matrices, for example, it is desirable to transfer such electrical, mechanical, and optical properties to bulk materials via the chemical modification of nanomaterial surfaces and edges to promote or enhance specific interactions or bonding strength between the matrix and the functionalized nanomaterial.